New filter and the fish are struggling for oxygen

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Hi, we moved into our new house in February of this year - this has a large (to my eyes) pond that is approx 4 * 7 m oval shape - between 0.5 & 1m deep - with shallower shelves. This has a pump that drives water to a water feature, followed by a much smaller pond ("the wildlife pond") & then back into the main pond. The pump is driven from a mains extension - so is not always on.

The fish woke up in spring & the water got murkier & murkier - so we tried adding plants & running the pump for a while. After running the pump, we decided that the small middle pond could not take the full flow of water without washing all the plants away, so I split the flow - such that some of it goes directly back into the main pond & some of it goes to the top.

We were running the pump occasionally - certainly not daily & certainly not all the time.

The fish looked healthy & more & more numerous but we only ever saw them for a couple of minutes a day when we feed them - so I added a filter (Swell pressure filter).

The water seemed to be clearing albeit quite slowly - but I expected that as I think the pump is undersized for the pond size - but if I go for a complete water change every 90 minutes as recommended elsewhere, then we would have quite a torrent flowing - and we don't want that.

We have 1 ghost koi, 30 - 40 goldfish of medium size (15-25 cm) and quite a lot of much smaller fish (this year's young?)

I turned the pump off overnight last night & when I came down this morning, most of the fish were at the surface - apparently gasping. From what I can glean from the internet - this means they are short of oxygen. We cleaned the filter, added some hose water via a fine spray, turned the pump back on & it rained - so I'm quite happy they are ok again.

It seems as if the filter has upset whatever balance we had in the pond & removed some oxygenation capacity from it - such that we will now need to run the pump & filter continuously. Is this to be expected with a new filter? Will it improve again as the filter matures? Will I ever be able to turn off the pump again?

We have an obvious issue with overstocking - are there groups out there who are looking for replacement fish?

Many thanks for any input.
 
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Your pump/filter should be running 24/7. You should try to get the water returning to the pond to splash or disrupt the surface to help with oxygenation. Or better yet, get an aerator with one or two air stones.
 

mrsclem

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Hi, we moved into our new house in February of this year - this has a large (to my eyes) pond that is approx 4 * 7 m oval shape - between 0.5 & 1m deep - with shallower shelves. This has a pump that drives water to a water feature, followed by a much smaller pond ("the wildlife pond") & then back into the main pond. The pump is driven from a mains extension - so is not always on.

The fish woke up in spring & the water got murkier & murkier - so we tried adding plants & running the pump for a while. After running the pump, we decided that the small middle pond could not take the full flow of water without washing all the plants away, so I split the flow - such that some of it goes directly back into the main pond & some of it goes to the top.

We were running the pump occasionally - certainly not daily & certainly not all the time.

The fish looked healthy & more & more numerous but we only ever saw them for a couple of minutes a day when we feed them - so I added a filter (Swell pressure filter).

The water seemed to be clearing albeit quite slowly - but I expected that as I think the pump is undersized for the pond size - but if I go for a complete water change every 90 minutes as recommended elsewhere, then we would have quite a torrent flowing - and we don't want that.

We have 1 ghost koi, 30 - 40 goldfish of medium size (15-25 cm) and quite a lot of much smaller fish (this year's young?)

I turned the pump off overnight last night & when I came down this morning, most of the fish were at the surface - apparently gasping. From what I can glean from the internet - this means they are short of oxygen. We cleaned the filter, added some hose water via a fine spray, turned the pump back on & it rained - so I'm quite happy they are ok again.

It seems as if the filter has upset whatever balance we had in the pond & removed some oxygenation capacity from it - such that we will now need to run the pump & filter continuously. Is this to be expected with a new filter? Will it improve again as the filter matures? Will I ever be able to turn off the pump again?

We have an obvious issue with overstocking - are there groups out there who are looking for replacement fish?

Many thanks for any input.
Don't know if you have Craigslist or something similar there to advertise for homes for your fish. It does sound like you are overstocked. Put flyers up at your local garden centers as well.
 

j.w

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@Keefe
24/7 on the pump running!
 
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Thanks to everybody for the welcome and the input.
I'm interested in the apparent change from a pond that didn't seem to need a pump and filter running to one that seems to need a pump and filter running 24/7 as a result of me trying to improve the pond's ecological balance.
I've read a little bit about "natural ponds" - which I guess have a much lower fish load - and maybe we would get more tadpoles living to maturity.
 
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I hope your hose water is not chlorinated. Most central water systems are. Or maybe you have well water?

If your water is in fact treated, you need to get a dechlorinizer/conditioner to make it safe for fish, plants and beneficial bacteria colony.

If your filter has both pads and some sort of bio media, you should only be rinsing the pads, never the bio media. You should be using water that is not chlorinated to rinse the pads. You can use pond water in a bucket. The reason you never clean the bio media is because you don't want to disturb the beneficial bacteria colony.

There is also a bio film growing all over everything in your pond. All over the liner, etc. You don't want to disturb that either. No power washing or regularly emptying and cleaning the pond.
 

mrsclem

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I doubt that the filter use caused your issue. Most likely, your pond has now exceeded the fish load limit. Fish grow and reproduce, so a pond with no filter and a few fish may be fine for a while but sooner or later, problems will occur.
 

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